Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2007
Publication Date: 1/1/2008
Citation: Cowger, C., Weisz, R. 2008. Blends of Soft Red Winter Wheat Varieties Increased Yield in North Carolina. Agronomy Journal. 100:169-177. Interpretive Summary: Seed mixtures, or blends, of small grains are commonly grown in the U.S. Pacific Northwest and in Kansas in order to stabilize yields and manage diseases. A field experiment was conducted at three North Carolina locations in each of two years to determine if winter wheat blends may offer advantages to southeastern U.S. producers. Blends significantly outyielded the means of the pure varieties in them at Plymouth in 2006 and across all environments in the experiment, with a mean overall blend advantage of 0.13 Mg/ha. Yield stability of blends was greater than that of pure varieties. Quality characteristics generally did not differ significantly between blends and pure varieties, but the seed diameter of blends was significantly less uniform than that of pure varieties. Wheat blends may offer a modest yield advantage to North Carolina growers even in the absence of severe disease epidemics.
Technical Abstract: Seed mixtures, or blends, of small grain cultivars have been widely used to manage foliar fungal diseases and stabilize yield. However, blends are unknown in eastern U.S. wheat production, where numerous diseases and abiotic stresses often take a toll. In 2004-05 and 2005-06, a field experiment was conducted at Kinston, Plymouth, and Salisbury, NC, to compare performance of eight soft red winter wheat cultivars having a range of maturities with that of 13 blends, each consisting of equal proportions of two or three of the cultivars. The blends were composed to have complementary disease resistance traits. In each site-year, the entire experiment was conducted in two adjacent trials, one with 20.4 m2 plots and other with 1.1 m2 plots. Plots of barley were planted with the wheat in a checkerboard design to minimize interplot interference. Pressure from any airborne or soilborne disease was at most moderate in any site-year. Blends significantly outyielded the means of their respective components (mid-components) in Plymouth in 2006 (P = 0.042) and across all site years (P = 0.039), with a mean overall blend advantage of 0.13 Mg/ha. Averaged across site-years, two blends significantly outyielded their mid-components: NC Neuse / USG 3592 (P = 0.032) and McCormick / NC Neuse / Roane (P = 0.011). In individual site-years, blends outyielded mid-components in six cases among four site-years. Mid-components outyielded blends in two cases, both at Salisbury in 2006. Yield stability of blends exceeded that of pure varieties by the stability variance model and principal component analysis. In general, blends did not differ significantly from mid-components for test weight, protein content, hardness, or falling number (sprouting tolerance), but seed diameter non-uniformity of blends exceeded that of mid-components. Soft wheat blends may offer a small yield advantage to North Carolina growers in the absence of severe disease.